1. Field of the Invention
The present invention relates to a catheter to be inserted into a body lumen, vessel or duct such as a blood vessel for use. The present invention also relates to a balloon catheter having a balloon in the distal end portion thereof, and particularly, to a rapid-exchange type balloon catheter.
2. Description of the Related Art
In recent years, intravascular operations have been widely performed to treat a lesion part of a blood vessel by inserting a catheter into the blood vessel percutaneously without carrying out a surgical operation. In these operations, a catheter must be selectively inserted into an intricately bending, meandering or branching narrow blood vessel to position its distal end portion at the targeted site.
In general, in order to insert a catheter into the blood vessel percutaneously, the catheter is made to reach the targeted site while a guide wire (introduction aid tool) is inserted into the lumen of the catheter. On this occasion, generally, the catheter is preceded by a guide wire and advanced to the target site in the blood vessel.
To guide the catheter having the guide wire inserted therein into the targeted site of the body, the operation of moving forward or backward or turning the guide wire and the catheter is carried out from an end side in vitro thereof. This operation must be transmitted to the distal end side of the catheter without fail. Therefore, torque transmissibility and pushability are required for the catheter.
When the body portion (catheter body) of a relatively thin catheter having a small diameter to be applied to a narrow blood vessel is made from a synthetic resin material, it may have low stiffness or be readily kinked, whereby the above-mentioned torque transmissibility and pushability may not be obtained fully. Therefore, the catheter body of the relatively narrow catheter is made of a metal tube having bending elasticity.
However, when the catheter body is made of a metal tube, the distal end side portion of the catheter body especially has too high flexural rigidity and lacks flexibility. Therefore, it is inferior in follow-up ability (followability) which enables it to follow the preceding guide wire in the winding blood vessel smoothly and reliably.
A balloon catheter to be inserted into the blood vessel typified by a catheter used for PTCA (Percutaneous Transluminal Coronary Angioplasty) (to be referred to as “PTCA catheter” hereinafter) has a guide wire lumen for inserting a guide wire which is formed along the entire length of the catheter in addition to a balloon lumen for inflating the balloon. Prior to the insertion of the catheter into the blood vessel, the guide wire is inserted into the guide wire lumen and the distal end portion of the guide wire is guided to the targeted site (near a stricture in the blood vessel) together with the catheter in such a manner that the distal end of the guide wire precedes the catheter.
There are many variations of the PTCA catheter which differ in the size of a balloon to be suited to a case of a disease such as the size of the stricture site and the diameter of the blood vessel or to expand the stricture site stepwise. After insertion into the blood vessel, the work of exchanging the PTCA catheter may be necessary. Even when a plurality of indwelling units for securing an inner diameter in the blood vessel, called “stent”, are installed, the catheter may be removed from and inserted into the blood vessel several times.
The exchange of the catheter described above is preferably carried out while the guide wire is left in the blood vessel to reduce a burden on a patient, the operation time and the labor, to prevent infection, or the like.
However, since the guide wire lumen is formed along the entire length of the conventional catheter as described above, in order to exchange the catheter from the in-vitro end side (proximal end side) of the guide wire while the guide wire is left in the blood vessel, the in-vitro end of the guide wire must be projected from the proximal end of the catheter to a length longer than the total length of the catheter. That is, the length of the guide wire must be twice or more the length of the catheter and there is a problem that such long projecting guide wire reduces ease of the operation.
There is proposed a rapid-exchange type catheter having a guide wire lumen formed only in the distal end portion of the catheter, that is, a catheter in which an opening at the distal end of the catheter communicates with a side hole formed at a position several centimeters away from the opening toward the proximal end and this short lumen is engaged with a guide wire (EP 0397357 A1 (JP 4-9548 B)). This catheter can be exchanged while the guide wire is left in the blood vessel without projecting the in-vitro end of the guide wire long from the proximal end of the catheter.
In order to guide the catheter to the targeted site in vivo while the guide wire is inserted in the guide wire lumen, as the blood vessel meanders, the guide wire and the catheter must conform to the curvature of the meandering blood vessel. In order to conform to this curvature, the operation of moving forward or backward or turning the guide wire and the catheter is carried out on the in-vitro end side. This operation must be transmitted to the distal end side of the catheter without fail. To this end, torque transmissibility, pushability and kink resistance are required for the catheter.
When the body portion (catheter body) of a relatively small catheter to be applied to a narrow blood vessel is made from a synthetic resin material, it may have low stiffness and be readily kinked, whereby the above-mentioned torque transmissibility and pushability may not be obtained fully. Therefore, the catheter body of the relatively small catheter is made of a metal tube having bending elasticity.
However, when the catheter body is made of a metal tube, the distal end side portion of the catheter body especially has too high flexural rigidity and lacks flexibility. Therefore, it is inferior in follow-up ability (followability) which enables it to follow the preceding guide wire in the winding blood vessel smoothly and reliably.